As per the documentation, you need to specify true as the second argument if you want an associative array instead of an object from json_decode. This would be the code:

$result = json_decode($jsondata, true);

If you want integer keys instead of whatever the property names are:

$result = array_values(json_decode($jsondata, true));

However, with your current decode you just access it as an object:

print_r($obj->Result);

json_decode() does so work. The second param turns the result in to an array:

var_dump(json_decode('[{"a":"b"},{"c":"d"},{"e":"f"}]', true));

// gives

array(3) {
  [0]=>
  array(1) {
    ["a"]=>
    string(1) "b"
  }
  [1]=>
  array(1) {
    ["c"]=>
    string(1) "d"
  }
  [2]=>
  array(1) {
    ["e"]=>
    string(1) "f"
  }
}

I tried following code on PHP 5.6.11-1ubuntu3.1 (cli), and surprisingly got exactly what I wanted. Since this question is so old, I don't remember what was the PHP version when I tried this at the time of posting this code.

Code:

<?php
class Test {
        public $message = "this is message";
        public $number = 10;
}
$t1 = new Test();
$t2 = new Test();
$arr = array(0 => $t1, 1 => $t2);
$json_data = json_encode($arr);
var_dump($json_data);
$original_array = json_decode($json_data, true);
$original_object = json_decode($json_data, false);
var_dump($original_array);
var_dump($original_object);
?>

The output I get is:

string(85) "[{"message":"this is message","number":10},{"message":"this is message","number":10}]"
array(2) {
  [0]=>
  array(2) {
    ["message"]=>
    string(15) "this is message"
    ["number"]=>
    int(10)
  }
  [1]=>
  array(2) {
    ["message"]=>
    string(15) "this is message"
    ["number"]=>
    int(10)
  }
}
array(2) {
  [0]=>
  object(stdClass)#3 (2) {
    ["message"]=>
    string(15) "this is message"
    ["number"]=>
    int(10)
  }
  [1]=>
  object(stdClass)#4 (2) {
    ["message"]=>
    string(15) "this is message"
    ["number"]=>
    int(10)
  }
}

Give this a try:

$json = '
{
   "article_details":[  
      {  
         "article_code ":"000000000300028156 ",
         "diff_amnt ":"1 "
      },
      {  
         "article_code ":"000000000300028174 ",
         "diff_amnt ":"1 "
      },
      {  
         "article_code ":"000000000300028126 ",
         "diff_amnt ":"1 "
      }
   ],
   "article":[  
      {  
         "article_code ":"000000000300028156 ",
         "diff_amnt ":"1 "
      },
      {  
         "article_code ":"000000000300028174 ",
         "diff_amnt ":"1 "
      },
      {  
         "article_code ":"000000000300028126 ",
         "diff_amnt ":"1 "
      }
   ]
}';

$key = 'article_code '; // Since your key is 'article_code ' but not 'article_code', I have to do this
$dataObject = json_decode($json);
echo $dataObject->article_details[0]->$key; // This will out put: 000000000300028156 
$dataArray = json_decode($json, true);
echo $dataArray['article_details'][0]['article_code ']; // This will out put: 000000000300028156 

$myArray = json_decode($json, true);

var_dump($myArray['id']);
var_dump($myArray['user'][0]['fname']);

Do this:

$value = json_decode($mku, true)[1];

The second parameter of json_decode determines whether to return the result as an array instead of an object. Since you set it to true your result is an array and not an object.

$content = $final_res['articles'][0]['Content'];

Use json_decode()

$json = '[
{ "firstName":"John" , "lastName":"Doe" }, 
{ "firstName":"Anna" , "lastName":"Smith" }, 
{ "firstName":"Peter" , "lastName":"Jones" }
]';
$json_decoded = json_decode($json);
var_dump($json_decoded);

See it in action